Distribution of load to peripheral facilities of a packet-based switching system

ABSTRACT

The invention relates to a distribution of load to peripheral adaptation units of a packet-based switching system, whereby the peripheral adaptation units serve as an interface between the packet-based switching center and a packet-based communications network. According to the invention, a load that accrues in the switching center is statically or dynamically distributed to the peripheral adaptation units by a load distributor. This enables the periphery adaptation units to be utilized whereby preventing wiring-related overloads and, in addition, being able to take different performance capacities of the peripheral adaptation units into account. When at least one additional switching center is provided upstream, a load budget concerning its use of the peripheral adaptation units can be transmitted thereto from the packet-based switching center. The load distribution is adapted in the event of hardware failures and signaling interferences.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International ApplicationNo. PCT/DE03/00740, filed March 7, 2003 and claims the benefit thereof.The International Application claims the benefits of German applicationNo. 10212374.8 filed Mar. 20, 2002, both of the applications areincorporated by reference herein in their entirety.

FIELD OF INVENTION

The present invention relates to a method for administering apacket-based switch in which peripheral adaptation units are used as theinterface between a packet-based communications network and applicationsof said switch. The applications perform communications and signalingtasks. The invention further relates to an arrangement for administeringa packet-based switch in which peripheral adaptation units are used asthe interface between a packet-based communications network andapplications of said switch, said applications performing communicationsand signaling tasks.

BACKGROUND OF INVENTION

The background of the invention is the area of connection between timedivision multiplex-based communications networks known from conventionaltelephony, and communications networks in which packet-based networktechnologies are employed, e.g. implemented in an Internet Protocol(IP)—or ATM-based network. In the course of the convergence of these twotypes of network, adaptations are required both at the subscriber endand on the switching side. A time division multiplex-based switchprovides call control and the termination and through-connection of theuser channels. A switch in a packet-based communications networkcontrols the connections and the associated user channels routed outsidethe switch.

SUMMARY OF INVENTION

The task of the invention is to provide an improved load distribution toperipheral devices of a packet-based switching system. This isimplemented, for example, by means of gateways or resource servers whichconstitute interfaces for user data streams and control between diversenetworks. The user data streams can be controlled, for example, by theReal Time Transport Protocol (RTP), a data transport protocol for thetransmission of audio and video data. Control can be provided, forexample, by the Media Gateway Control Protocol (MGCP) or by the H.323protocol, an international standard for voice, data and videocommunication over packet-based networks.

As well as the conventional analog and ISDN terminals and extensions,terminals suitable for connecting to the packet network and permittingbroadband access but additionally supporting the well-known basicfeatures of telephone networks are possible as terminating equipment,using, for example, the H.323 Protocol or also the Session InitiationProtocol (SIP), an application layer signaling control protocol withwhich multimedia sessions are set up, maintained and terminated. Obviouschoices as access medium to the subscriber are both subscriber linesdesigned for xDSL (Digital Subscriber Line) and the already widespreadcable networks. By means of subscriber-end adaptation devices, such asan Integrated Access Device (IAD) or Multimedia Terminal Adapter (MTA)for terminating said access networks, it is possible to connect bothbroadband customer premises equipment (e.g. PC with Internet access,television receiver, video telephone), and to provide access forconventional subscriber terminal equipment (for example, analogtelephone, ISDN telephone, analog or ISDN extension).

Message-based interoffice signaling likewise takes place via thepacket-based network (e.g. by means of H.323), provided packet-basedswitches are involved. If another switch is time divisionmultiplex-based, signaling is performed using the signaling methodcustomary in ISDN/PSTN networks, e.g. by means of country-specificvariants of the ISDN User Part Protocol. A signaling gateway forconverting the signaling may be necessary. The transition of the userdata stream between the time division multiplex- and the packet-basednetwork is through a media gateway controlled by the packet-basedswitch.

Because of the plurality of specific protocols and the different typesof communicating parties, the packet-based switch is equipped withfunctions known as applications which relate to intercommunication withother time division multiplex- or packet-based switches (virtualtrunking), processing of analog and ISDN signaling of conventionalsubscribers connected on a packet basis (e.g. Voice over DSL (VoDSL),Voice over Cable) or processing of signaling of packet-based subscribers(for example, H.323, SIP). For all call requests, the packet-basedswitch generally provides means for suitable interworking of theapplications. These are selected according to the destinationscorresponding to the dialing information, so as to replicate thefamiliar functions and characteristics of conventional telephony in thepacket-based environment for both subscribers and network operators.

So-called peripheral adaptation units are used as physical interfacesbetween the packet-based switch and the packet-based communicationsnetwork. These are assigned to specific peripheral devices of theswitching system which control the switching sequences of certainsubscribers or trunk sets. The peripheral adaptation units generate orreceive the signaling—on an application-specific basis—and control thethrough-connection of the user data stream. In general a plurality ofapplications (application mix) can be simultaneously active on aperipheral application unit, resulting in application-specific capacityutilizations for a peripheral adaptation unit. At least some of theapplications communicate directly with other switches. One such otherswitch can be present e.g. in the form of an upstream switch or anH.323-compliant gatekeeper.

The assignment between the trunks and/or trunk groups with theapplications defined thereon and the peripheral adaptation units iscreated by a load distributor in the central unit of the packet-basedswitch. This assignment can be quasi statically preset or is performeddynamically according to the capacity utilization and any failuresituations of the hardware of the peripheral adaptation units. Ingeneral, therefore, the applications are temporarily connected viaperipheral adaptation units to other switches via the hardware of thesame peripheral adaptation unit.

It is possible to provide switching for packet-based subscribers if theyare using a signaling protocol commonly employed in the packet-basednetwork, such as the H.323 protocol in the IP-based network. This isperformed by modeling of the subscriber as part of a concentratorinterface of the packet-based switch. Gatekeepers necessary forauthorization and having access to the H.323 subscribers of a switchthen act as upstream switches, a plurality of peripheral adaptationunits generally being assigned to a single gatekeeper in each case. Theperipheral adaptation units treat the gatekeepers like H.323 gatewaysand therefore register cyclically with ‘their’ gatekeeper. If they failto register, the gatekeeper concludes that the peripheral adaptationunit has failed. The A-side seizures (seizures in the direction of theswitch) are distributed to the assigned peripheral adaptation units on acall by call basis without taking account of the loading of theperipheral adaptation units and the performance provided by thehardware.

Conventional subscribers can be connected to a packet network via aperipheral subscriber terminating equipment, their signaling can beforwarded in a packet-based manner to a switch equipped with a suitableadaptation unit where it can be used for call control for thesubscriber. More specifically the Stream Control Transmission Protocolis accordingly used to transport the ISDN signaling. The abovementionedtechnical problem does not occur, as no upstream switch exists for thisapplication, instead all the ports of the applications are used directlyvia two peripheral adaptation units used in active/standby mode for A-and B-side seizures.

For reasons of reliably accessibility, upstream switches can generallyselect from a plurality of peripheral adaptation units of said switch(redundant access). This means that at least some of the peripheraladaptation units appear to the upstream switch as a set of signalinggateways for the relevant application. On seizure of the packet-basedswitch by an upstream switch, selection from a plurality of peripheraladaptation units is consequently possible. However, because of theapplication mix and their generally different performancecharacteristics, these have different capabilities in respect ofhandling a call request. In the case of a seizure performed by thepacket-based switch itself, the problem of even capacity utilization ofthe peripheral adaptation units can be solved, as the capacityutilization of the peripheral adaptation units is known locally. In thecase of a seizure in the direction of said switch, however, there is nomeasure for the time-dependent size of the performance margins of theperipheral adaptation units as a decision criterion for selecting theperipheral adaptation unit to be seized in the upstream switch.

The object of the invention is to improve the loading of peripheraladaptation units in a packet-based switch.

More specifically, the peripheral adaptation units shall be loaded on anapplication-specific basis in such a way that redundant access to theperipheral adaptation units is possible in both directions (to and fromthe switch) as part of the options provided by the hardware. Duringnormal operation, if no failure is present, the load resulting fromseizures by the packet-based switch and/or by one or more upstreamswitches shall be distributed to the peripheral adaptation units in sucha way that as far as possible none of the peripheral adaptation units isoverloaded, thereby supporting an application mix on the peripheraladaptation units with simultaneous use of hardware of differingcapability, i.e. different performances of the peripheral adaptationunits. A hardware failure shall be tolerated without overloading of aperipheral adaptation unit by the switches involved. Overload handlingin the sense of forcing communications traffic back to the periphery ofthe packet-based switch shall be made possible.

These objects are achieved by the features set forth in the claims.

According to the invention, in a packet-based switch the capacityutilizations of the peripheral adaptation units are determined by acentral unit and, on the basis of said capacity utilizations,assignments are created between the trunks and/or trunk groups with theapplications defined thereon and the peripheral adaptation units.

More specifically, load indicators are determined which take intoaccount—on an application-specific basis—the resource requirement of theapplications and the individual capacity utilizations, the spareresources and the performances of the peripheral adaptation units.

The load indicators can be determined, for example, with the aid of CPUcapacity utilization, utilization of operating system resources or sizeof significant queues.

In terms of planning, the resources must be designed in such a way thatthe demand resulting from the applications is smaller than thecorresponding application-specific resources available.

The assignment must be organized in such a way that the load resultingfrom seizures, taking the load indicators into account, is distributedas evenly as possible to the peripheral adaptation units.

Determination of the load indicators and any re-assignment of the trunksto the peripheral adaptation units taking said load indicators intoaccount can also take place dynamically, i.e. in small predefined timeintervals, for example.

The load indicators are optionally communicated to the upstream switchor switches after assignment, so that in such an upstream switch theresulting load in the direction of said switch can be distributed to theperipheral adaptation units taking the load indicators into account.

The load indicators can be communicated to the upstream switches e.g. aspart of the signaling or cyclically repeated registration (see H.323) orby means of an additional communications or control interface.

In the packet-based switch, a load budget can be optionally determinedfor each of the peripheral adaptation units, said load budget can beappropriately distributed to upstream switches according to capacityutilization criteria and the partial load budget information can becommunicated to the upstream switches.

There, this partial load budget information is then in turn used todistribute the load to the peripheral adaptation units of said switch.

Optionally said switch's peripheral adaptation unit last seized by saidswitch can be used for a new seizure—on an application-specific basis—bythe upstream switch.

After a settling time, the subscriber assignment of the peripheraladaptation units set by the load distributing function becomesestablished for bilateral seizures. In this case the exchange of loadbudget information between the switches is unnecessary.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, advantages and characteristics will now be explainedin a detailed description of embodiments with reference to the Figuresof the accompanying drawings in which:

FIG. 1 shows the bidirectional access to peripheral adaptation units;

FIG. 2 shows the signaling of the H.323 budgets;

FIG. 3 shows the signaling of the budgets with added margins;

FIG. 4 shows a subscriber-specific approximation of A- and B-sideselection of the peripheral adaptation units;

FIG. 5 shows the case of two upstream H.323 gatekeepers;

FIG. 6 shows a failure of an interfaces unit when two upstream H.323gatekeepers exist and

FIG. 7 shows a failure of a gatekeeper when two upstream H.323gatekeepers exist.

DETAILED DESCRIPTION OF INVENTION

In FIG. 1 the described parts relating to the invention areschematically illustrated. It shows a packet-based switch 1, the loaddistributing function 2 as part of the coordination processor 11, theswitch's peripheral devices for call processing of part of thesubscribers and trunks 12 in each case and which are provided e.g. forcertain subscriber sets 10 in each case and are designed for certainapplications 3 in each case. The applications 3 are active on aplurality of peripheral adaptation units 4. The assignment between theswitch's peripheral devices 12 which are designed for certainapplications and the peripheral adaptation units 4 are symbolized byarrows 7. The peripheral adaptation units 4 form the interface to thepacket-based communications network 5. Additionally visible are twoupstream switches 6 which access the peripheral adaptation units 4. Thisaccess is symbolized by further arrows 8. The upstream switches areresponsible for certain trunk or subscriber totalities 9.

An embodiment of the invention will now be explained in greater detailwith reference to FIGS. 2 and 3. FIG. 2 shows the method on the basis ofa switch 1 which is designed among other things for an H.323 useraccess. This example can be implemented analogously for a SIP subscriberaccess. The packet-based switch 1 contains peripheral devices withapplication-specific switching tasks for a certain subset of theperiphery of the switching system. In the example illustrated, theapplications supported are the three applications 3 H.323, VirtualTrunking (VT) and VoDSL. A total of five subscriber totalities 10 areavailable to the peripheral devices designed for these applications.

There is additionally a totality of trunks of the Virtual Trunkingapplication.

The applications 3 are active on four so-called packet managers 4functioning here as peripheral adaptation units. In the example shown,the assignment of the peripheral devices 12 designed for theseapplications to the packet Managers 4 for the VoDSL application isperformed statically, VoDSL being assigned to the packet managersnumbers three and four. For the H.323 and VT applications, theassignment is performed dynamically by the central load distributor 2which is part of the coordination processor 11.

The coordination processor 11 communicates to the peripheral devices 12designed for the relevant application the packet managers 4 assigned tothem. This is represented by further arrows 14. In the example all fourpacket managers 4 are designed for the H.323 application, the packetmanager number two additionally for the VT application and the packetmanagers numbers three and four for the H.323 und VoDSL applications.

The load distributor 2 determines load indicators for each packetmanager 4 on an application-specific basis and send them to the packetmanagers 4. This is represented by a further arrow 13. These loadindicators are specified in FIG. 2 on an application-specific basis as apercentage of the capacity of a packet manager 4. The assignment betweenthe applications on the peripheral devices of the switching system 12and the packet managers 4 is symbolically represented by arrows 7.

The assignment between the H.323 and VT applications and the packetmanagers 4 is performed dynamically, and therefore generally changes atcertain time intervals.

FIG. 2 therefore shows a momentary assignment state characterized inthat, for B-side seizures of one of the peripheral devices 12 numbersone to eight providing the H.323 application, one of the packet managersnumbers one to three is used, as the packet manager number four has beenassigned 0% by the load distributor 2 as load indicator for the H.323application.

The packet managers 4 therefore constitute the physical interface to thepacket-based communications network 5 and via the latter to a gatekeeper6 functioning as an upstream switch. The gatekeeper serves the H.323subscriber totalities 9 which are assigned to the peripheral devicesnumbers one to eight. The packet managers 4 are used by the gatekeeper 6as gateways and normally register cyclically with the gatekeeper 6. Aspart of this registration they communicate to the gatekeeper 6 the loadindicators temporarily assigned to them, shown here specifically for theH.323 application. This is indicated by arrows 15 from the packetmanagers 4 to the gatekeeper 6. This ensures that in the event of achange in the assignment between the peripheral devices 12 for the H.323application and the packet managers 4, the load indicators arecommunicated to the gatekeeper 6 in an uncomplicated manner. For B-sidecalls (performed by the switch 1), a peripheral device and applicationassigned to the relevant subscribers is used and therefore the packetmanager 4 assigned by the load distributor 2 is used for the signalingto the gatekeeper 6. This means that it is not necessary to decideseparately for each call which of the packet managers 4 is to be used.

FIG. 3 shows the optional case in which the load budgets communicated tothe upstream gatekeepers 6 are selected larger than resulting from theoriginal load distribution. This constitutes an option for the case ofthere being budget margins on the packet managers 4 which can beprovided e.g. by underwiring or because of unused redundancy.

The following FIGS. 4 to 7 contain the same components as FIG. 2. Unlessotherwise described below, the same conditions apply to FIGS. 4 to 7 asin FIG. 2.

According to FIG. 4, the forward signaling of the load indicators by thepacket managers 4 to the gatekeeper 6 can be dispensed with if thepacket manager 4 via which a B-side seizure for an H.323 subscriber lastoccurred is registered with the gatekeeper 6 and if that packet manageris used for A-side seizure of that subscriber. After a certain settlingtime, for A- and B-side seizures by H.323 subscribers, this methodproduces a capacity utilization of the packet managers 4 correspondingto the load indicators specified by the load distributor 2 for thepacket managers 4. In the example, the subscriber sets 10 numbers oneand four have been momentarily assigned the packet manager 4 number oneby the load distributor/coordination processor 2. Correspondingly, thesubscriber set 10 number two is assigned the packet manager 4 number twoand the subscriber set 10 number three is assigned the packet manager 4number three. The four subscriber sets 9 are served by the gatekeeper 6and have already adjusted to the same assignment. This proceduresimplifies the engineering of the packet-based switch 1, as theconditions of conventional concentrator interfaces are replicated inwhich the signaling of subscribers always takes place via the sameperipheral components of the switching system.

FIG. 5 shows an example for the scenario with two gatekeepers 6. Thegatekeeper 6 number one has access to the packet managers 4 numbers oneand three, whereas the gatekeeper 6 number two has access to the packetmanagers 4 numbers three and four. In this case a load budget isdetermined in switch 1 for each packet manager 4 on the basis of theload indicators. This load budget is then signaled to the gatekeepers 6in a manner analogous to that described above as part of the cyclicalregistration of the packet managers 4 and is then in turn used fordeciding which of the packet managers 4 is to be used for A-sideseizures.

FIG. 6 schematically illustrates how, following hardware failure of thepacket manager 4 number two, the assignments between the peripheraldevices and their applications 12 and the packet managers 4 can berestored by the load distributor 2. In the example shown, the H.323subscriber seizures processed prior to the failure by the packet manager4 number two (load indicator 15%) are taken over by the packet manager 4number four after the failure. Similarly, the VT seizures processedprior to the failure by the packet manager 4 number two (load indicator20%) are taken over by the packet manager 4 number one after thefailure.

Because packet manager 4 number two has not registered, the gatekeeper 6number has decided that it has failed and will therefore not use itagain for the time being. Only the packet manager 4 number one is nowavailable to the gatekeeper 6 number one as a communication connectionto switch 1 for H.323 seizures.

FIG. 7 illustrates hardware failure of the gatekeeper 6 number one. Thisfailure is revealed to switch 1 by the loss of communication/signaling.The load distributor then uses only the packet managers 4 numbers threeand four for the new assignments of all trunks for H.323 subscribers, asthese packet managers are connected to the operational gatekeeper 6number two.

The advantages of the invention may be summarized as follows:

-   -   Comprehensive load distribution to the interfaces units        (peripheral adaptation units) by means of a single load        distribution algorithm and therefore avoidance of uncoordinated        load from the periphery of the packet-based switch    -   Optionally additional support of dynamically determined load        indicators for load distribution    -   Can also be used in multi-homing scenarios in which, as seen        from an upstream or remote packet-based switch, selection from a        plurality of packet-based switches equipped with peripheral        adaptation units is possible    -   Simplified engineering of the switch due to the fact that, with        predictable loading during undisturbed normal operation and in        standby mode, e.g. in the event of hardware failures, the        assignment of subscribers and trunks is reduced to the        assignment of hardware units to the applications and        intercommunication of the peripheral adaptation units    -   Dynamically favorable load distribution from the viewpoint of        the packet-based switch, as distribution to a plurality of        peripheral adaptation units does not have to be decided on a per        call or per signaling message basis    -   Easy allowance for peripheral adaptation units of differing        performance.

1-17. (canceled)
 18. A method for load distribution in a packet-basedswitch in which peripheral adaptation units are used as the interfacebetween a packet-based communications network and applications of theswitch, the method comprising: performing communication and/or signalingtasks by the applications; determining the individual workloads of theperipheral adaptation units; and forming an assignment between theapplications and the peripheral adaptation units depending on thedetermined workloads.
 19. A method according to claim 18, furthercomprising: determining load indicators for the peripheral adaptationunits in the switch on an application-specific basis depending on theresource requirement of the applications, and/or the individualworkload, and/or the spare resources, and/or the performance of theperipheral adaptation unit; and using the load indicators for theassignment between the applications and the peripheral adaptation units.20. A method according to claim 19, wherein the load indicators aredetermined by using the CPU workload and/or the workload of operatingsystem resources and/or the size of significant queues.
 21. A methodaccording to claim 18, wherein the resources of the peripheraladaptation units exceed or do not cover the resource requirement of theapplications assigned to them.
 22. A method according to claim 19,wherein at least some of the load indicators are determined dynamicallyand any re-assignment of the applications to the peripheral adaptationunits is performed dynamically taking said load indicators into account.23. A method according to claim 19, wherein the load indicators arecommunicated to at least one of the upstream switches and that at leastone upstream switch distributes the load produced in the direction ofthe switch to the peripheral adaptation units taking into account theload indicators communicated to it.
 24. A method according to claim 23,wherein the information is communicated to the upstream switches as partof the signaling or of the cyclically repeated registration or by anadditional communication or control interface.
 25. A method according toclaim 19, further comprising: generating a load budget for at least oneof the peripheral adaptation units as a function of the load indicators;distributing the load budget among the upstream switches in the form ofpartial load budget information; and distributing the load produced inthe direction of the switch to the peripheral adaptation units by theupstream switches using the partial load budget information.
 26. Amethod according to claim 18, wherein, in the case of a new seizure of asubscriber or trunk, switches upstream of the packet-based switch seize,on an application-specific basis, the peripheral adaptation unit lastused by the switch to seize said subscriber or said trunk.
 27. A methodaccording to claim 18, wherein, in the event of failure of at least oneof the peripheral adaptation units, and/or applications, and/or upstreamswitches, a re-assignment between the applications and the peripheraladaptation units takes place.
 28. An arrangement for load distributionin a packet-based switch in which peripheral adaptation units are usedas interface between a packet-based communications network andapplications of the switch, wherein the applications performingcommunication and/or signaling tasks, the arrangement comprising: amechanism for determining the individual workloads of the peripheraladaptation units and for distributing the load to the peripheraladaptation units taking the individual workloads determined intoaccount.
 29. An arrangement according to claim 28, further comprising: amechanism for determining individual, application-specific loadindicators for the peripheral adaptation units as a function of theresource requirement of the applications, and/or the workload, and/orspare resources, and/or performance of the peripheral adaptation unit;and a mechanism for assignment between the applications and theperipheral adaptation units using the load indicators.
 30. Anarrangement according to claim 28, further comprising: a mechanism fordynamically recording the load indicators and for dynamicallyre-assigning the applications to the peripheral adaptation units usingthe load indicators.
 31. An arrangement according to claim 28, furthercomprising: a mechanism for communicating the load indicators from theswitch to at least one of the upstream switches; and a mechanism fordistributing the load produced in the upstream switch in the directionof the to the peripheral adaptation units of the switch taking the loadindicators into account.
 32. An arrangement according to claim 28,further comprising: a mechanism for generating individual load budgetsfor at least one of the peripheral adaptation units as a function of theload indicators, for distributing said load budget to the upstreamswitches in the form of partial load budget information and fordistributing the load produced in the upstream switch in the directionof the switch to the peripheral adaptation units of the switch using thepartial load budget information.
 33. An arrangement according to claim28, further comprising: a mechanism for application-specific seizure ofthe peripheral adaptation unit last used by the switch for thesubscriber or trunk to be seized, the mechanism being used by theupstream switch.
 34. An arrangement according to claim 28, furthercomprising: a mechanism for re-assignment between the applications andthe peripheral adaptation units in the event of failure of at least oneof the peripheral adaptation units, and/or applications, and/or upstreamswitches.